Midnight Compact Language

Complete guide to writing privacy-preserving smart contracts with Compact.

What is Compact?

Compact is a purpose-built programming language for zero-knowledge smart contracts. Unlike adapting existing languages, Compact was designed from scratch to make privacy-preserving programming natural and secure.

Key Design Goals:

• Compile directly to efficient ZK circuits
• Type-safe cryptographic operations
• Familiar syntax for developers
• Automatic proof generation

Quick Start

Basic Contract Structure

circuit myContract(private secretInput, public publicInput) {
  // Private data hidden in proof
  // Public data visible to all
  // Proof shows execution was correct
}

Project Scaffolding

Use scripts/init-compact-project.py to create new projects with proper structure.

Contract Generation

Use scripts/generate-contract.py to generate boilerplate from templates.

Compilation

Use scripts/compile-compact.py for compilation with error handling.

Language Reference

Basics

See language-basics.md for:

• Syntax and structure
• Types and variables
• Functions and control flow
• Modules and imports

ZK Patterns

See zk-patterns.md for:

• Common zero-knowledge proof patterns
• Circuit optimization techniques
• Performance best practices
• Privacy-preserving algorithms

Standard Library

See standard-library.md for:

• Built-in cryptographic functions
• Hashing and commitments
• Elliptic curve operations
• Blockchain interaction primitives

Contract Examples

See contract-examples.md for annotated examples:

• Private token contracts (Zswap integration)
• Voting contracts (secret ballot)
• DeFi contracts (confidential trading)
• Identity contracts (credential verification)

Best Practices

See best-practices.md for:

• Security guidelines
• Performance optimization
• Testing strategies
• Formal verification approaches

Contract Templates

Ready-to-use templates in assets/templates/:

• basic-contract/: Minimal working contract
• private-token/: Zswap token implementation
• voting-contract/: Private voting system
• defi-contract/: Confidential DeFi protocol

Development Workflow

1. Initialize: python scripts/init-compact-project.py <project-name>
2. Generate: python scripts/generate-contract.py <template-name>
3. Develop: Write contract logic in Compact
4. Compile: python scripts/compile-compact.py <contract-file>
5. Test: Run tests with Compact test framework
6. Deploy: Deploy to Midnight network

Resources

• Official Docs: https://docs.midnight.network/develop/reference/compact/
• Language Reference: https://docs.midnight.network/develop/reference/compact/lang-ref
• Standard Library: https://docs.midnight.network/develop/reference/compact/compact-std-library/
• Grammar Spec: https://docs.midnight.network/develop/reference/compact/compact-grammar